MIT discovers ocean microbe that produces biofuel from sunlight

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MIT is making progress researching common bacterium with the potential to revolutionize the biofuels industry. A microorganism called Prochlorococcus, the most abundant photosynthetic organism on Earth, has been shown to hold and release small, oil-bound sacs of material into the open ocean. Though the researchers have no idea why the bacterium might do this, from the perspective of survival, they aren’t looking this gift-horse in the mouth; what they have found is an organism that is seemingly tailor-made for use on the industrial scale.

See, most biofuels are created or collected via death. We can pressure-cook algae into crude oil, then burn that oil as though it were extracted normally from the ground — so long as the carbon that makes up the algae was pulled from the atmosphere, we can re-release it back into the atmosphere and still call it “carbon neutral.” However, even when we’re using a single metabolic product of a microbe’s life cycle, we almost always have to kill the microbes to get at the goods — put a sample of biofuel-creating bacteria into a blender, break them all open, then do chemical separation to get out only our fuel chemical of interest.

Lead researchers Steven Biller (left) and Sallie “Penny” Chisholm.

This new study, however, shows that Prochlorococcus naturally buds off vesicles of fatty compounds. One researcher puts it bluntly: this bacteria is using sunlight to make organic carbon, then packing that carbon into vesicles and releasing it into the surrounding ocean. Since Prochlorococcus is one of the most widespread microorganisms on the planet, this has enormous implications for our understanding of ocean ecosystems and the carbon cycle. It’s also a compelling mystery in basic genetics and microbiology. It’s also a very obvious tool for exploitation by genetic engineers.

Prochlorococcus is actually one of the simplest, most elegantly streamlined organisms known to science; they generally have less than 2,000 genes in total, having pared down any extraneous DNA that wasn’t directly necessary to its fairly simply photosynthetic lifestyle. This implies two things. One: it should be fairly easy to find and modify the genes that make and inject the fatty compounds into the vesicles, and Two: vesicle release must be, somehow, very important to the bacterium’s life strategy.

The potential of “constitutive release” of biofuels is enormous. No longer would we have to create biofuels in “batches,” like fermenting casks of beer; properly designed collection rigs could both maintain bacterial populations and collect their vesicle-bound products. This is the sort of functionality that scientists might consider trying to clone into existing industrial species — and here it’s been found already in existence. It’s hard to imagine a species better-suited to biofuel production, either; Prochlorococcus is already photosynthetic, already makes and releases some products into solution, and it does so with a minimum of fuss or complication. Though the vesicles were only discovered about 8 years ago, Prochlorococcus is actually one of the best studied microorganisms of all.

A regular biofuel extraction setup. It’s bulky, expensive, and slow — but perhaps not for long.

Of course, that’s not to say that we’ll necessarily be using Prochlorococcus as our biofuel production species. Just as likely, the mechanism of filling and releasing vesicles will be studied, stolen, and regifted to a totally different model species. Rather than inducing this vesicle-producing bacterium to create useful biofuels, we may induce biofuel-producing species to produce vesicles. Either way, there’s the potential for an enormous improvement in production efficiency.

While the researchers certainly don’t know why Prochlorococcus would choose to naturally give away a large amount of chemical energy, they do of course have some ideas. One idea is that the vesicles act as a natural defense against phages, while another says that its streamlined genome can no longer detoxify its internal environment, thus requiring the bacteria to export certain molecules as they are created. Still another idea is that the vesicles assist with genetic transfer between bacteria, a simple version of bacterial sex that helps introduce some variety into the species’ meta-genome.

Whatever the reason for its quirk, Prochlorococcus will be the topic of serious study in biofuels labs around the world. However it ends up being used, what we have here is an incredibly useful and powerful way of streamlining biofuel production. Whether it’s ethanol, diesel, or something entirely new, this breakthrough has a good chance of being a part of any successful future biofuels project.